Lathe turret

ABSTRACT

In the lathe turret construction disclosed herein, indexing of the turret to bring successive tools into operating position is accomplished by a separate locking member which is axially slidable, relative to the turret spindle, between a locking position and a release position. The separate locking member includes means for preventing rotation with respect to a fixed frame of reference, independent of the member in which the turret spindle is journaled.

United States Patent Mclver, Sr. 1 July 18, 1972 54] LATHE TURRET2,908,195 10/1959 Benes ..74/826 x [72] Inventor: Clement L. Mclver,Sr., Wayland, Mass. a Examiner wiuiam E 013 73 nee: I ed 8 AssistantExaminer-F. D. Shoemaker l g corpora u my Mass Attorney-Kenway, Jenneyand l-lildreth [22] Filed: July 29, 1970 [21] Appl. No.: 59,048 [57] ABSCT in the lathe turret construction disclosed herein, indexing of theturret to bring successive tools into operating position is U.S. L, m lihed a e arate locking member i5 axially 82/ 36 A slidable, relative tothe turret spindle, between a locking posi- 111% t 29/32 tion and arelease position. The separate locking member in [58] Field of Search..74/826, 818, 813 L, 813 R, eludes means for preventing rotation withrespect to a fixed 74/824; 82/36 A; 279/5 frame of reference,independent of the member in which the turret spindle is journaled. 56 Rf Ci I 1 e 7 Clairm, 4 Drawing Figures UNITED STATES PATENTS 2,975,6573/1961 Samuel ..74/826 X 4 3% n5 T 95 FIOI 59 3| J h 29 57 5| T g 4. I73 L /97 6| 75 57 l |3l Y 19 e3 45 77 47 53 8| e3 7. I32 43 A v M W [1 I65 p 1 ,Il 4,; (72 7.) 'v/l/f/y zf g i iii 1 I 7 9160 \X, so

PATENTED JUL1 8l972 3.677'1 0- snsn 1 OF 2 FIG! INVENTOR CLEMENT L.MCIVER ATTORNEYS PATENIED Jun 8 m2 SHEET 2 [1F 2 INVENTOR C LEMENT wig/HBY H M W ATTORNEYS LATHE TURRET BACKGROUND OF THE INVENTION Thisinvention relates to a lathe turret and more particularly to such aturret suitable for use in numerically controlled lathes providingexceptionally high precision.

In conventional turret lathes, the turret is indexed so as to bringsuccessive tools into operating position by first displacing the turretaxially, so as to move it out of engagement with a stationary lockingmember, and by then rotating it to bring the next tool into operatingposition. As the turret in such an arrangement must be journaled so asto permit both rotation and axial displacement, it has typically beendifficult to provide great precision in tool positioning.

Among the objects of the present invention may be noted the provision ofa lathe turret providing improved precision in tool positioning; theprovision of a turret which may be rotated in either direction and whichcan move more than one tool position at a time; the provision of such aturret in which journaling of the turret spindle for compound motion isnot required; the provision of such a turret which may rapidly operated;the provision of such a turret in which tool positioning accuracy doesnot deteriorate with use; the provision of such a turret which operatesreliably and which is of relatively simple and inexpensive construction.Other objects and features will be in part apparent and in part pointedout hereinafter.

SUMMARY OF THE INVENTION Briefly, the present invention provides meansfor accurately positioning a selected one of a plurality of operatingelements or tools at a predetermined operating position. The individualtools or operating elements are held in a turret which is mountedon aspindle adapted for rotation around a predetermined axis. The spindle isjoumaled in a tube or other journal member for rotation only, axialmovement of the spindle relative to the journal member being prevented.A locking member is provided which slides axially with respect to thespindle and which includes a plurality of locking surfaces adapted tointerfit with corresponding surfaces on the spindle in each of aplurality of preselected angular positions corresponding to thepositions of the various operating elements around the spindle axis.These surfaces prevent relative rotation of the spindle and lockingmember when the locking member is in a first axial position, relativerotational movement being permitted when the locking member is in asecond axial position. The locking member also includes means forpreventing rotation thereof with respect to a fixed frame of reference.Means are also provided for selectively moving the locking memberbetween its first and second positions and for rotating the spindle tobring successive operating elements into the operating position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a turretlathe provided with a turret assembly constructed in accordance with thepresent invention, showing a preferred arrangement of the turretassembly in relation to the other elements of the lathe.

FIG. 2 is a plan view, with parts broken away, of a lathe turretassembly of the present invention. FIG. 3 is a section substantially onthe line 33 of FIG. 2 and FIG. 4 is a section substantially on the line44 of FIG. 2.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, thereis indicated at 11 a turret lathe of a type generally adapted forautomatic operation, e.g., under numerical or so-called direct digitalcontrol. The main lathe spindle is indicated at 13 and carried a chuck15 adapted to receive a workpiece as is indicated at 17. A plurality oftools 21-26 for operating on the workpiece are mounted in a turret head29 of generally hexagonal shape. The entire turret assembly is in turnmounted on a carriage 31 which is adapted to be traversed longitudinallywith respect to the lathe spindle 13 on ways or guides 33 and 35, thetravel of the carriage being controlled by a lead screw 37. As isexplained in greater detail hereinafter, the turret is also mounted,relative to the carriage 31, so as to permit movement transverse to theaxis of rotation of the workpiece, i.e., toward and from the viewer asillustrated in FIG. 1. Thus, a selected one of the tools 21-26, broughtinto operating position by the turret, may be arbitrarily positionedwith respect to the rotating workpiece 17.

Referring now to FIGS. 2-4, the turret head 29, which incorporates aplurality of tool-holding sockets 41, is itself part of a spindleassembly, designated generally as 43. The head is mounted directly on aspindle shaft 44, being secured by a nut 45 and being keyed to the shaftas indicated at 47. The threaded end of shaft 44 is protected by a cap49. The spindle assembly 43 also includes a collar-like member 54, whichis keyed to the shaft 44 near its left-hand end as indicated at 53. Inthat the head 29, the shaft 44 and the collar member 54 are keyed,relative rotation is prevented and these elements together function as arigid unit. As is explained in greater detail hereinafter, the collarmember 54 is provided with locking surfaces which are employed inlocking the head in various angular positions so as to preciselyposition tools held in the sockets 41.

A second collar-like member 56 is mounted on the shaft 44 near itsrighbhand end, being secured by nuts 58.

The spindle assembly 43 is journaled within a turret tube or cartridgemember 51. This tube is also referred to hereinafter as a journalmember. At the left-hand end of the tube 51, the spindle is journaled bymeans of a pair of opposed taperedroller bearings 55 and 57, thesebearings being preloaded by means of a ring-like cap member 59 withsuitable shimming being provided as needed. The pre-loaded bearings 55and 57 serve to accurately position the turret head end of the spindleassembly 43 with respect to the tube or journal member 51. Rocking orcanting of the spindle 43 within the tube 51 is prevented by a thirdtapered-roller bearing 61 which operates between the other end of thetube 51 and the collar 56 at that end of the spindle 43.

The tube 51 is itself slidable within the carriage member 31, suitablescraper seals being provided as indicated at 60. Rotation of the tube 51within the carriage member 31 is prevented by a key 62 which is mountedon the carriage member 31 and which rides in a slot 64 in the tubemember. It should be noted at this point, however, that this sliding fitis not employed in the system of rotational locking which positions theturret head but rather this key way is used only for nominallypreventing rotation of the tube 51 itself. The sliding movement of thetube within the carriage member is controlled by a suitable lead screwsystem which is a part of the lathe mechanism and is thus not shown ordescribed in detail herein.

Between the two collar members 54 and 56 is a locking member 63 which isco-axial with the spindle shaft 44 and, as is explained in greaterdetail hereinafter, can slide axially relative to the spindle assembly43 and the spindle journal tube 51. As may be seen, a sliding seal isprovided between the spindle assembly 43 and the co-axial locking member63 at two points. At the left-hand end of the locking member, a slidingseal is provided by means of O-rings 65 between the locking member andthe relatively small diameter portion of the spindle shaft 44. At itsright-hand end a sliding seal is provided between the locking member 63and a larger diameter portion of the overall spindle assembly 43 bymeans of a hydraulic piston sealing ring 67, mounted on the collarmember 56, together with a back-up O-ring 69.

The locking member 63 is slidable between two operational positionsrelative to the spindle 43 and the journal tube 51. The first positionis the left hand or locking position and this is the positionillustrated in FIG. 2. In the second position, the locking member 63 isshifted slightly to the right with respect to the spindle assembly 43and the journal tube 51. The purpose of the locking member 63 is toprevent rotation of the spindle assembly when the locking member 63 isin its first or left-hand position. Interfitting locking surfaces areprovided by a plurality of hardened steel balls 73 which interact withcorresponding bores 75 and 77 in the opposed faces of the collar member54 and locking member 63 when the locking member is in its left-handposition. As may be more easily seen in FIG. 2, the bores 75 and 77 aresomewhat smaller in diameter than the balls 73 so that the engagingsurfaces are essentially conical in nature. Thus, when the lockingmember 63 and the collar member 54 are biased toward each other,clamping the balls 73 therebetween, the balls operate to essentiallylock the locking member and spindle together so that relative rotationis prevented. When the locking member 63 is in its right-hand position,however, the separation is sufficient to permit the spindle assembly 43,with its collar 54, to rotate to bring successive tool-holding sockets41 into operative position. As will be understood, the number ofmatching sets of opposed bores 75 and 77 and of hardened balls 73 willbe equal to the number of tool positions around the turret head 29,i.e., six in the embodiment shown.

A locating ring or race 87 is provided for maintaining each locking ball73 generally in alignment with a respective one of the bores 77.Rotation of the ring itself is prevented by a succession of pins 89which link the ring 87 to the locking member 63. As it is desirable thatthe balls 73 be free to rotate, clamping of the balls between the ring87 and the locking member is prevented by springs 91 which bias the ring87 away from the locking member when the locking member is moved to itsright-hand or second position.

While the locking member 63 is illustrated in its left-hand or lockingposition, it is normally biased towards its right-hand position, as seenin FIG. 2, by means of a coil spring 79. The left-hand end of spring 79bears against the spindle collar member 54 through an intermediatesleeve 81, while the righthand end of the spring bears against thelocking member 63 through an intermediate sleeve 83 and a ball bearing85. The bearing prevents the applying of torque to the coil spring 79when the spindle rotates.

The locking member 63 carries a tang 95 which is secured thereto bymeans of socket screws 97. The general function of the tang 95 is toprevent rotation of the locking member with respect to a relativelyfixed frame of reference. As noted previously, the arrangement of theoverall lathe mechanism 11 is such that the entire turret assembly,including the tube member 51 within which the turret spindle 43 isjournaled, may be arbitrarily positioned with respect to the rotatingworkpiece 17. Accordingly, the tube 51 is not a suitably stable frame ofreference for angular position. Rather, the tang passes through anopening 99 in the tube member 51 which provides liberal clearance,allowing the tube to move freely with the locking member 63 as thelocking member is slid between its first and second positions relativeto the spindle assembly 43. Projecting from the tube 51, the tang 95slides between a pair of precisely ground ways 101 and 103 which aremounted on the carriage 31. Preferably the ways 101 and 103 are mounted,as illustrated in FIG. 4, in a mating tapered slot 105 in the carriagemember 31 by means of pins 107 and cap screws 111, so that the clearancebetween the tang and the ways may be precisely adjusted. While thecarriage member 31 may be movable in the sense that it moves withrespect to the overall lathe assembly 11, it constitutes a relativelyfixed frame of reference with respect to the movements of the turret 29as its rotates around its axis to bring successive tools into operativeoperating position and also with respect to the longitudinal movement ofthe entire turret assembly with the journal tube 51.

As may be seen in FIG. 2, the tang 95 is provided with the central bore113 through which hydraulic fluid may be provided under pressure to thelocking member 63. For this purpose, the outer end of the bore 113 istapped, as indicated at 115, to receive a conventional hydraulicfitting. The opposite end of the tang includes a cylindrical boss 117which is sealed to the locking member 63 by an O-ring 119. The bore 113communicates with the interior of the locking member 63 between the twopoints at which it is slidingly sealed to the coaxial spindle assembly43.

The portion of the locking member 63 between the O-rings 65 and thepiston seal 67 either provides clearance around the spindle, asindicated at 121, or incorporates passages, as indicated at 123, so thatthere is free hydraulic communication in this region between the twosets of sliding seals. Since the locking member 63 is slidingly sealedto the spindle assembly at portions thereof which are of differentdiameter, it can be seen that the locking member and spindle assemblytogether in effect form a hydraulic piston and cylinder in which theeffective area of the piston is equal to the difference between thecross-sectional areas of the two different portions of the spindleassembly.

As noted previously, the locking member 63 is normally biased to itsright-hand position by the coil spring 79. However, as may be seen inFIG. 2, movement in this direction reduces the effective volume of thehydraulic piston formed between the spindle 43 and the locking member63. Conversely, it can thus be seen that the application of a sufiicienthydraulic pressure will drive the locking member to the left asillustrated in FIG. 2, i.e., its locking position as describedpreviously. The release of such pressure will allow the locking memberto again move to its second or right-hand position under the bias of thespring 79.

A gear 131 is keyed to the end of the spindle 43 opposite the turret 29.This gear provides a means through which the spindle may be rotated,e.g., by a digital stepping motor 132, driving a meshing gear 134, topermit successive tools held in the turret head 29 to be brought intooperative position when the locking member 63 is in its release orright-hand position.

In summary, the operation of the turret assembly is as follows. With thehydraulic pressure released from the interior of the locking member 63,the locking member is moved to the right by the spring 79. With thelocking member in its righthand position, the tool holding turret 29 isunlocked and may be rotated around the spindle axis, e.g., by thestepping motor 131, to any desired position so as to bring a selectedtool into operating position. As may be seen, there is no constraintupon either the direction of rotation or the number of tool positionswhich can be incremented at one time.

Once the desired tool has been brought into position, hydraulic pressureis applied to the interior of the locking number 63, forcing it to theleft so that the hardened balls 73 lock the locking member and thespindle assembly together as an effectively rigid element. Rotation ofthis rigid combination is prevented by the tang 95. As noted previously,the tang prevents rotation with respect to a relatively fixed frame ofreference, i.e. the ways 101 and 103 which are mounted on the carriage31. Since the axis of the spindle is positioned relative to the journaltube 51 by the pre-loaded bearings 55, 57 and 61, which do not have toaccommodate any relative axial movement between the spindle and thejournal member, highly accurate positioning of the selected tool isassured. Further, the absence of any axial movement of the turretspindle relative to the tube within which the spindle is journaledfacilitates the elimination of foreign matter from the bearings andother locating surfaces though not all of the seals which serve thisfunction have been described in detail. This is in contrast to the usualturret indexing systems in which the locating surfaces are relativelyexposed when the turret is moved axially to release the locking system.Likewise, the absence of any bearing surfaces which must accommodate acompound movement, i.e. a combination of axial and rotational movementsgreatly reduces wear which would affect the accuracy of toolpositioning.

Since the hardened steel balls 73 and the matching bores 75 and 77 serveonly as locking surfaces and do not act as bearing surfaces duringindexing of the turret, they are capable of providing an exceptionallyaccurate and reproduceable positioning operation. Further, since theengaging surfaces are aproximately conical in nature, the long-termwearing-in or seating of these balls into the bores actually tends toimprove the short-term accuracy which may be obtained over any givenproduction or manufacturing operation. In other words, the workingaccuracy which can be obtained may actually tend to improve during thelife of the turret rather than deteriorate. Thus, it is desirable toprovide a running-in procedure during which the turret is indexedrandomly from one tool position to another, so as to provide an initialseating of the balls 73 against the ends of the bores 75 and 77.

In view of the foregoing, it may be seen that several objects of thepresent invention are achieved and other advantageous results have beenattained.

As various changes could be made in the above construction withoutdeparting from the scope of the invention, it should be understood thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:

1. Apparatus for accurately positioning a selected one of a plurality ofoperating elements at a predetermined operating position, said apparatuscomprising:

a spindle adapted for rotation around a predetermined axis;

a journal member in which said spindle is journaled for rotation aroundsaid axis only, axial movement being prevented;

a locking member which is slidable, relative to said journal memberaxially with respect to said spindle between first and second axialpositions, said locking member having a plurality of locking surfaceswhich are adapted to interfit with corresponding surfaces on saidspindle in each of a plurality of preselected angular positions of saidspindle when said locking member is in said first position, thereby toprevent relative rotation of said spindle and said locking member,relative rotation between said spindle and said locking member beingpermitted when said locking member is in its second said position, saidlocking member including also means for preventing rotation thereof withrespect to a relatively fixed frame of reference;

means for defining, together with said locking member and said spindle,a hydraulic cylinder for selectively moving said locking member betweenits first and second positions; spring opposing said hydraulic cylinder;and means by which said spindle can be rotated when said locking memberis in its second position, whereby successive operating elements can bebrought into said operating position without relative axial movementbetween said spindle and said journal member.

2. Apparatus as set forth in claim 1 wherein said locking surfacesinclude the ends of a plurality of bores in said locking member, theends of a matching plurality of bores in said spindle, and a matchingplurality of hard spherical members coacting between the ends ofrespective bores in said locking member and said spindle.

3. Apparatus as set forth in claim 1 including a stepping motor forrotating said spindle when said locking member is in said secondposition.

4. A lathe turret comprising:

a spindle having at one end thereof a head adapted to hold a pluralityof tools at respective angularly distributed positions around thespindle axis;

a tube within which said spindle is journaled for rotation around saidaxis, axial movement between said spindle and tube being prevented;

a support member within which said tube is axially slidable;

a locking member having a bore through which said spindle extends, theportion of said spindle passing through said locking member comprisingat least two cylindrical sec tions of different diameters;

means providing a sliding seal between said locking member and one ofsaid cylindrical spindle sections;

means providing a sliding seal between said locking member and the otherof said cylindrical spindle sections, said locking member being movablebetween first and second axial positions relative to said spindle, saidlocking member and said spindle having interfitting surfaces which mateat a plurality of relative angular positions corresponding to theplurality of tool positions around said spindle head and which preventrelative rotation of said spindle and locking member when said lockingmember is in said first axial position;

spring means biasing said locking member toward one of said axialpositions;

means for selectively providing hydraulic fluid under pressure betweenthe two said seals thereby to move said locking member to the other ofsaid axial positions;

a tang attached to said locking member and extending outside said tube;

guide means mounted on said support member for guiding said tang as saidtube slides in said support member for preventing rotation of saidlocking member relative to a said support member, independently of saidtube; and

means by which said spindle can be rotated when said locking member isin its second position, whereby successive tools can be brought into anaccurately predetermined operating position without axial movement ofsaid spindle relative to said tube.

5. A lathe turret comprising:

a spindle having at one end thereof a head adapted to hold a pluralityof tools at respective angularly distributed positions around thespindle axis;

a tube within which said spindle is journaled for rotation around saidaxis, axial movement between said spindle and tube being prevented;

a support member within which said tube is axially slidable;

a locking member having a bore through which said spindle extends, theportion of said spindle passing through said locking member comprisingat least a first cylindrical section of relatively small diameter and,toward the portion of said spindle opposite said head, a secondcylindrical section of relatively large diameter;

means providing a sliding seal between said locking member and saidfirst cylindrical spindle section;

means providing a sliding seal between said locking member and saidsecond cylindrical spindle section, said locking member being movablebetween first and second axial positions relative to said spindle, saidspindle having also means of defining a shoulder facing said lockingmember, said shoulder and said locking member each having a plurality ofopposing bores angularly distributed around their opposing surfaces atpositions corresponding to the tool positions around said spindle head;

a plurality of locking balls each of which is adapted to engage the endsof a pair of said opposed bores in said locking member and the shoulderon said spindle when said spindle is angularly positioned to place oneof said operating elements at said operating position and when saidlocking member is in said first position, thereby to lock said spindleagainst rotation relative to said locking member;

spring means biasing said locking member toward second axial position;

means for selectively providing hydraulic fluid under pressure betweenthe two said seals thereby to move said locking member to said firstaxial position, thereby to selectively lock said spindle againstrotation;

a tang attached to said locking member and extending outside said tube;

guide means mounted on said support member for guiding said tang as saidtube slides in said support member thereby to prevent rotation of saidlocking member relative to a said support member, independently of saidtube; and

means by which said spindle can be rotated when said 6. A turret as setforth in claim including a key mounted hydraulic pressure is releasedand said locking member is on said support member and sliding in alongitudinal slot in in its second position, whereby successive toolscan be said tube for Preventing l thereof: selectively brought into anaccurately predetermined A turret set forth 5 where-1n 331d pp operatingposition without axial movement of said spindle 5 member compnses alathe carnage relative to said tube

1. Apparatus for accurately positioning a selected one of a plurality ofoperating elements at a predetermined operating position, said apparatuscomprising: a spindle adapted for rotation around a predetermined axis;a journal member in which said spindle is journaled for rotation aroundsaid axis only, axial movement being prevented; a locking member whichis slidable, relative to said journal member axially with respect tosaid spindle between first and second axial positions, said lockingmember having a plurality of locking surfaces which are adapted tointerfit with corresponding surfaces on said spindle in each of aplurality of preselected angular positions of said spindle when saidlocking member is in said first position, thereby to prevent relativerotation of said spindle and said locking member, relative rotationbetween said spindle and said locking member being permitted when saidlocking member is in its second said position, said locking memberincluding also means for preventing rotation thereof with respect to arelatively fixed frame of reference; means for defining, together withsaid locking member and said spindle, a hydraulic cylinder forselectively moving said locking member between its first and secondpositions; a spring opposing said hydraulic cylinder; and means by whichsaid spindle can be rotated when said locking member is in its secondposition, whereby successive operating elements can be brought into saidoperating position without relative axial movement between said spindleand said journal member.
 2. Apparatus as set forth in claim 1 whereinsaid locking surfaces include the ends of a plurality of bores in saidlocking member, the ends of a matching plurality of bores in saidspindle, and a matching plurality of hard spherical members coactingbetween the ends of respective bores in said locking member and saidspindle.
 3. Apparatus as set forth in claim 1 including a stepping motorfor rotating said spindle when said locking member is in said secondposition.
 4. A lathe turret comprising: a spindle having at one endthereof a head adapted to hold a plurality of tools at respectiveangularly distributed positions around the spindle axis; a tube withinwhich said spindle is journaled for rotation around said axis, axialmovement between said spindle and tube being prevented; a support memberwithin which said tube is axially slidable; a locking member having abore through which said spindle extends, the portion of said spindlepassing through said locking member comprising at least two cylindricalsections of different diameters; means providing a sliding seal betweensaid locking member and one of said cylindrical spindle sections; meansproviding a sliding seal between said locking member and the other ofsaid cylindrical spindle sections, said locking member being movablebetween first and second axial positions relative to said spindle, saidlocking member and said spindle having interfitting surfaces which mateat a plurality of relative angular positions corresponding to theplurality of tool positions around said spindle head and which preventrelative rotation of said spindle and locking member when said lockingmember is in said first axial position; spring means biasing saidlocking member toward one of said axial positions; means for selectivelyproviding hydraulic fluid under pressure between the two said sealsthereby to move said locking member to the other of said axialpositions; a tang attached to said locking member and extending outsidesaid tube; guide means mounted on said support member for guiding saidtang as said tube slides in said support member for preventing rotationof said locking member relative to a said support member, independentlyof said tube; and means by which said spindle can be rotated when saidlocking member is in its second position, whereby successive tools canbe brought into an accurately predetermined operating position withoutaxial movement of said spindle relative to said tube.
 5. A lathe turretcomprising: a spindle having at one end thereof a head adapted to hold aplurality of tools at respective angularly distributed positions aroundthe spindle axis; a tube within which said spindle is journaled forrotation around said axis, axial movement between said spindle and tubebeing prevented; a support member within which said tube is axiallyslidable; a locking member having a bore through which said spindleextends, the portion of said spindle passing through said locking membercomprising at least a first cylindrical section of relatively smalldiameter and, toward the portion of said spindle opposite said head, asecond cylindrical section of relatively large diameter; means providinga sliding seal between said locking member and said first cylindricalspindle section; means providing a sliding seal between said lockingmember and said second cylindrical spindle section, said locking memberbeing movable between first and second axial positions relaTive to saidspindle, said spindle having also means of defining a shoulder facingsaid locking member, said shoulder and said locking member each having aplurality of opposing bores angularly distributed around their opposingsurfaces at positions corresponding to the tool positions around saidspindle head; a plurality of locking balls each of which is adapted toengage the ends of a pair of said opposed bores in said locking memberand the shoulder on said spindle when said spindle is angularlypositioned to place one of said operating elements at said operatingposition and when said locking member is in said first position, therebyto lock said spindle against rotation relative to said locking member;spring means biasing said locking member toward second axial position;means for selectively providing hydraulic fluid under pressure betweenthe two said seals thereby to move said locking member to said firstaxial position, thereby to selectively lock said spindle againstrotation; a tang attached to said locking member and extending outsidesaid tube; guide means mounted on said support member for guiding saidtang as said tube slides in said support member thereby to preventrotation of said locking member relative to a said support member,independently of said tube; and means by which said spindle can berotated when said hydraulic pressure is released and said locking memberis in its second position, whereby successive tools can be selectivelybrought into an accurately predetermined operating position withoutaxial movement of said spindle relative to said tube.
 6. A turret as setforth in claim 5 including a key mounted on said support member andsliding in a longitudinal slot in said tube for preventing rotationthereof.
 7. A turret as set forth in claim 5 wherein said support membercomprises a lathe carriage.